This application is based on Patent Application No. 11-325795 filed Nov. 16, 2000 in Japan, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a card connector for connecting an IC card to electronic devices, such as cellular phones, telephones, PDAs (personal digital assistance), portable audio devices and cameras, and more specifically to a card detect switch for a card connector which checks for the presence or absence of an IC card.
2. Description of the Related Art
In electronic devices such as cellular phones, telephones, PDAs and cameras, a variety of functions are added by inserting an IC card with a built-in memory or control IC, such as a SIM (subscriber identity module) card, an MMC (multimedia card), a Smart Media (trademark) card and an SD (secure digital or super density) card.
In a connector structure for removably inserting such an IC card, a plurality of contact terminals made of a metal leaf spring are provided in a connector housing to make contact with a plurality of contact pads formed on the front or back surface of the inserted IC card, so that the IC card is electrically connected to the electronic device having that connector. The contact pads of the IC card include a power supply pad connected to a power supply line and a plurality of signal pads for transmitting/receiving various signals. These contact pads are connected via the contact terminals of the card connector to a power supply circuit and various signal process circuits in the electronic device.
In the electronic devices that insert the IC card of this kind, there are many occasions where the user wishes to check whether the card is inserted or not. To meet this requirement a card detect switch needs to be provided in the card connector to check for the presence or absence of the inserted card.
A possible sensor structure for this purpose may include a light sensing type. The light sensing type, however, cannot be expected to provide a satisfactory level of detection precision as the card is becoming smaller in size and thickness. Another problem of the light sensing type is that the placement of an optical sensor becomes a hindrance to reductions in size and cost. Thus a technique utilizing the contact/separation of a contact leaf spring is considered the most promising system overall.
The conventional card detect switch using the contact leaf spring has the following construction, for example.
The card detect switch has two metal pieces installed inside an abutment wall against which the front face of the card inserted in the card connector is pressed. For example, one of the metal pieces is a cantilevered contact leaf spring that elastically deforms in the card insertion direction and the other metal piece is a stationary metal switch component with which a contact portion of the contact leaf spring is come into or out of contact. When the card is not inserted, the contact leaf spring and the stationary switch component are parted. When the card is inserted, the pressing force of the front face of the card elastically deforms the contact leaf spring, causing the contact portion of the contact leaf spring to be pressed against the stationary switch component.
In this way, the conventional switch structure elastically deforms the contact leaf spring in the card insertion direction to press it against the stationary switch component to come them into contact with each other. In other words, in the conventional structure, the contact pressure between the two metal pieces is secured by the pressing force in the card insertion direction.
In the switch structure of this kind, an appropriate contact pressure between the two metal pieces is required to ensure an electrical stability of the switch when closed. In the conventional structure described above, because the contact pressure between the two metal pieces is secured by the pressing force of the card in the card insertion direction, the final card insertion position in the connector is set so that the contact leaf spring is pushed a small distance (a fraction of a millimeter) from the position where the both metal pieces start contacting each other, in order to produce an appropriate contact pressure.
Hence, in the conventional art, the contact leaf spring is additionally deformed elastically by the distance mentioned above and the resulting reactionary force acts on the card. The recovery force of the contact leaf spring may become too large, resulting in the inserted card coming out easily. Thus, a countermeasure needs to be taken, such as the provision of a brake piece for preventing the card from coming off.
The present invention has been accomplished under these circumstances to solve these problems and provides a card detect switch of a card connector that prevents an inserted card from coming off and securely holds it.
When viewed from one aspect, the present invention provides a card detect switch of a card connector for checking the insertion of a card into the card connector according to whether two metal pieces that respond to the insertion/retraction of the card engage or disengage, comprising: a first metal piece elastically deformable in a card insertion direction and in a card thickness direction and having a first contact surface disposed almost parallel to top and bottom surfaces of the card being inserted; and a second metal piece having a second contact surface almost parallel to the first contact surface; wherein when the card is inserted, the first contact surface of the first metal piece that is elastically deformable in the card insertion direction and the second contact surface of the second metal piece are brought into sliding contact.
In this invention, when the card is inserted, the first metal piece elastically deforms in the card insertion direction. As a result of this elastic deformation, the contact surface of the first metal piece moves to a position of the second contact surface of the second metal piece. Then, the first contact surface and the second contact surface come into sliding contact with each other. The first and second contact surfaces are arranged perpendicular to the card thickness direction, so that the two metal pieces engage each other with a pressing force acting in the card thickness direction, i.e., in the connector height direction.
When viewed from another aspect, the present invention provides a card detect switch of a card connector for checking the insertion of a card into the card connector according to whether two metal pieces that respond to the insertion/retraction of the card engage or disengage, the card detect switch comprising: a first metal piece elastically deformable in a card insertion direction and in a card width direction and having a first contact surface disposed almost perpendicular to top and bottom surfaces of the card being inserted; and a second metal piece having a second contact surface almost parallel to the first contact surface; wherein when the card is inserted, the first contact surface of the first metal piece that is elastically deformable in the card insertion direction and the second contact surface of the second metal piece are brought into sliding contact.
In this invention, because the first and second contact surfaces are arranged perpendicular to the card width direction, the two metal pieces engage each other with a pressing force acting in the card width direction, i.e., in the connector width direction.
As described above, a predetermined contact pressure required between the first and second metal pieces when they engage is produced by a pressing force of the two metal pieces acting either in the connector height direction (card thickness direction) or in the connector width direction (card width direction). In this invention, therefore, there is no need to additionally deform the first metal piece elastically, as is required with the conventional art, to produce a required contact pressure. This in turn prevents the reactionary force of the first metal piece from becoming too large. As a result, this invention eliminates the need to provide a brake piece for preventing the card from coming off and thus can stably and reliably hold the card in the connector.